1. Field of the Invention
The present invention relates to a reproducing apparatus and, more particularly, to a reproducing apparatus having a multi-rotary-head device having n number of rotary heads (n being 3 or greater) for reproducing signals from a recording medium which has a multiplicity of parallel tracks.
2. Description of the Related Art:
Helical-scan type magnetic recording and reproducing apparatus have been known which have rotary video heads capable of recording and reproducing video signals in and from video tracks which are formed in a magnetic tape at an inclination to the longitudinal axis of the magnetic tape. This type of apparatus essentially requires tracking control for enabling the rotary video head to accurately scan the video track during recording and reproduction, and various tracking control systems have been proposed up to now.
In general, a recording and reproducing apparatus employing such a tracking control is arranged to enable the rotary heads to perform self-recording/reproduction, i.e., such that a signal from a track is reproduced by the same rotary head as that used for recording the signal in this track. Namely, in a magnetic recording and reproducing apparatus employing a plurality of rotary heads, errors are inevitably involved in regard to the positions of the heads relative to one another, track widths of the rotary heads, and so forth, so that the recording and reproducing performance is seriously impaired when recording and reproduction of a signal in and from a track are performed by different rotary heads.
In recent years, multi-channel rotary-head type recording and reproducing apparatus, capable of simultaneously recording or reproducing signals of a plurality of channels, have been developed for use in digital VTRs (DVTR).
In general, a video signal is a wide-band signal so that a huge amount of data per unit time is produced when the video signal is digitized. It is difficult to magnetically record and reproduce such a huge amount of digital data in a serial manner. To overcome this difficulty, it has been proposed to use multi-channel type system for handling these video data so that each channel has a reduced data rate. This is the reason why the multi-channel recording and reproduction system is used in DVTRs.
The above-mentioned self-recording/reproduction is more significant when used in DVTRs employing the multi-channel recording and reproducing system because the use of different rotary heads for recording and reproduction of signals from a given track will cause a relative time-offset of the signals between recording and reproducing phases. DVTRs are required to be able to perform error correction by making use of signals reproduced from all the channels. The reproduced signals involving the above-mentioned time offset cannot be used for such error correction.
For this reason, in known DVTRs, it has been a common measure to conduct a tracking control so as to enable all the rotary heads to perform self-recording/reproduction, even when a large number of heads are employed.
An increase in the number of heads, however, undesirably prolongs the time till a tracking control drawing state is obtained. Namely, in the case of a DVTR having 8 heads, each head is aimed at only one out of 8 tracks so that a maximum mis-tracking amount is as large as .+-.4 tracks. Therefore, a considerably long time is required until the tracking control is drawn after start-up of the system or when the tracking control has failed for any reason. No video signal is reproduced during the tracking control so that a random image is displayed to discomfort the user.
The use of 8 heads also requires that the pattern of the recording signals for the tracking control is formed in 8-track period, so that the recording and reproducing circuits are complicated. In a system in which tracking control relies upon a pilot signal recorded in a portion of each track, problems are encountered not only in that the recording and reproducing circuits are complicated but also a large area of recording is occupied by the pilot signals, failing to meet demand for higher information recording density.
These problems become more serious as the number of the channels is increased, i.e., the number of tracks with which the signal processing has been completed. This makes it difficult to meet a future demand for higher recording density of signals of wide band.